1. Field of the Invention
The present invention relates to a method of driving a disc, and more particularly, to a method of detecting a disc using a ratio of peak-to-peak values of S-curves.
2. Description of the Related Art
An S-curve indicates a signal acquired from irregular reflection from a pit formed on a recording medium such as a DVD, when light is radiated on a recording surface of the recording medium. For DVDs, a single disc is distinguished from a dual disc by a magnitude of the S-curve signal or a number of S-curve signals. However, because the S-curve signal is not uniform due to a change in a quantity of light or a reflection factor of a pickup (not shown), an error occurs when detecting the disc.
FIGS. 1A and 1B are flowcharts of a conventional method to detect the disc. FIG. 1A shows a method to detect the disc based on the number of S-curve signals. The number of S-curve signals is detected at operations 100a and 102a. If the number of S-curve signals is 1, the disc is detected as the single disc and a setting is performed at operation 103a. If the number of S-curve signals is 2, the disc is detected as the dual disc and the setting is performed at operation 104a. If an S-curve is not detected at operation 100a, an error occurs in a disc detection at operation 101a. FIG. 1B shows a method to detect the disc based on the magnitude of the S-curve signal. The magnitude of the S-curve signal is detected at operations 100b and 102b. If the magnitude of the S-curve signal is at least 2V, the disc is detected as the single disc and setting is performed at operation 103b. If the magnitude of the S-curve signal is less than 2V, the disc is detected as the dual disc and setting is performed at operation 104b. If the magnitude of the S-curve signal does not exceed 200 mV at operation 100b, the disc error is detected at operation 101b. Because the reflection factor of the dual disc is less than that of the single disc by 40–60%, the magnitude of an S-curve signal detected through the pickup from the dual disc is less than that from the single disc. FIG. 2A is a diagram of a waveform when the disc is detected as the single disc. The number of S-curve signals is 1, and the magnitude of the S-curve signal is at least 2V. FIG. 2B is a diagram of a waveform when the disc is detected as the dual disc. The number of S-curve signals is 2, and the magnitude of the S-curve signals is less than 2V.
Because the S-curve signal S_CURVE is not uniform due to a change in the quantity of light or reflection factor of the pickup, a single/dual disc detection error may occur as shown in FIGS. 2C and 2D. Referring to FIG. 2C, the disc may be detected as the single disc based on the number of S-curve signals but may be detected as the dual disc based on the magnitude of the S-curve signal. Referring to FIG. 2D, the disc may be detected as the dual disc based on the number of S-curve signals but may be detected as the single disc based on the magnitude of the S-curve signals. In the case of a DVD+RW and a DVD−RW, as shown in FIGS. 2E (DVD+RW) and 2F (DVD−RW), the disc may be detected as the dual disc based on the magnitude of the S-curve signal but may be detected as the single disc because the number of S-curve signals is 1. Accordingly, it is difficult to detect the disc.